Method for minimizing oxidation in positive displacement casting

ABSTRACT

An improved method for positive displacement casting and/or for positive displacement bonding and, more particularly, for automatically forming, on a continuous, reproducible basis, fusion bonds devoid of structural, electrical and cosmetic defects between two or more workpieces by: (1) moving a heated electrode into the area to be bonded so as to uniformly heat and melt the portions of the workpieces to be bonded; (2) while, at the same time, displacing substantially all of the molten material from the area to be bonded into a storage area or reservoir surrounding the heated electrode where such molten material is maintained in its uniformly heated molten state, and (3) neutralizing and/or entraining oxidants present and removing the same from the bond area; and, (4) then retracting the electrode so as to permit the molten material to return to the cavity formed by the electrode in the workpieces where such molten material is allowed to cool and solidify, thus forming a flawless bond between the workpieces-thermal or fusion bonds are made in accordance with the methods of the invention by a combination of (1) elevated temperature levels sufficient to melt the material to be bonded, and (2) displacement of the molten material; as contrasted with more conventional techniques and/or apparatus which combine elevated temperature levels and pressure.

United States Patent 1191 1111 3,908,741

Keizer v Sept. 30, 1975 METHOD FOR MINIMIZING OXIDATION [57] ABSTRACT IN POSITIVE DISPLACEMENT CASTING An improved method for positive displacement casting [75] Inventor: Alan Keizer Huntingdon Valley and/or for positive displacement bonding and, more particularly, for automatically forming, on a continu- [73] Assignee; Gou|d Inc St Paul, Minn ous, reproducible basis, fusion bonds devoid of structural, electrical and cosmetic defects between two or [22] Flled: 1974 more workpieces by: (1) moving a heated electrode [21 APPL 435,179 7 into the area to be bonded so as to uniformly heat and melt the portions of the workpieces to be bonded; (2) while, at the same time, displacing substantially all of [52] 164/80; 164/1 10 the molten material from the area to be bonded into a [51] CL- B22D 25/04; BJK 1 1/00 storage area or reservoir surrounding the heated elec- [58] Flew of Search 164/80 l trode where such molten material is maintained in its 164/D1G' 1; 29/486 uniformly heated molten state, and (3) neutralizing 475, 494, 495; 136/176, 134 R, 168; 21 and/0r entraining oxidants present and removing the 86; 228/45 58 'same from the bond area; and, (4) then retracting the electrode so as to permit the molten material to return [561 References Cited to the cavity formed bythe electrode in the work- UNITED STATES PATENTS 7 pieces where such molten material is allowed to cool 2,045,523 6/1936 Fassler 219/86 and solidify, thus forming a flawless bond betweenthe 2,053,417 9/1936 Brace 29/494 workpieces-thermal or fusion bonds are made in ac- 3,1)71,852 1/1963 ROgCl'S 29/494 X cordance with the methods of the invention by a com- 3 3 3/1963 sciflky 219/86 bination of (l) elevated temperature levels sufficient 3,767,889 10/1973 Szmo B11 211. 136/134 R to melt the material to be bonded and displacc ment of the molten material; as contrasted with'more Pnmml" "7 Husar conventional techniques and/or apparatus which com- Emmmflcarl Rowold bine elevated temperature levels and pressure. I Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Volt & Osanm l0 Claims, 23 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 of 13 3,908,741

(Pi/ A Aer) US. Patent S ept.30,1975 Sheet20f 13 3,908,741

U.S. Patnt Sept. 30,1975 Sheet4of 13 3,908,741

US. Patent Sept. 30,1975 Sheet70f13 3,908,741

U.S., Patent Sept. 30,1975 Sheet9of 13 3,908,741

US. Patent Sept. 30,1975 Sheet 10 0f13 3,908,741

RELATED APPLICATIONS Robert Holbrook Cushman, Ser. No. 435,157, filed Jan. 21, 1974; Raymond L. Schenk, Jr., Ser. No. 435,178, filed Jan. 21, 1974; Robert I-Iolbrook Cushman and Raymond L. Schenk, Jr., Ser. No. 435,169, filed Jan. 21, 1974; Raymond L. Schenk, Jr. and Alan S, Kei'zer, Ser. No. 435,160, filed Jan. 21, 1974; Raymond L. Schenk, Jr., Robert Holbrook Cushman and Alan S. Keizer, Ser. No. 435,180, filed Jan. 21, 1974; Kurt R. Stirner and Robert Holbrook Cushman, Ser. No. 435,172, filed Jan. 21, 1974; Raymond L. Schenk, Jr., and John A. Bruzas, Ser. No. 435,181, filed Jan. 21 1974; Raymond -L., Schenk, Jr., John .A. Bruzas and William E. Coville, Ser. No. 435,182 filed Jan. 21, 1974; John A. Bruzas and William E. Coville, Ser. No. 435,l56, filed Jan. 21, 1974; Raymond L. Schenk, Jr. and William B. Hayes, Ser. No. 435,166, filed Jan. 21",

BACKGROUND OF THE INVENTION The present invention relates in'general to fusion casting, and/or to fusion bonding or thermo bonding of two or more workpieces and, more particularly, to methods characterized by their ability to automatically form, on a continuous, reproducible, high speed, production-line basis, cast parts having a desired shape, as well as fusion bonds devoid of structural, electrical and/or cosmetic defects between two or more work pieces by a technique hereinafter referred to as posigether;including,' merely;by way of example, welding, thermoecor'ripression bonding, I ultrasonic bonding, per -g;

' can be obtained, one is normally limited tothe amount;

of heat that can be applied and in the type of reducing tive displacement casting. It will become apparent as the ensuing description proceeds that the term casting is used herein in its broadest sense and encompasses the melting and shaping or reshaping of one or more parts into a single, unitary structure which may or may not be composite with an unaltered workpiece component, all by and with the positive displacement system disclosed herein. Thus, the phrase positive dis- 7 placement casting is intended herein to be generic to positive displacement bondingf ln its principal aspects, the invention is concerned with improved meth-,

ods for automatically moving a heated electrode through the portions of the workpiece(s) to be cast or bonded so as to uniformly heat and melt those portions of the workpiece(s) to be cast or bonded while, at the same time, displacing the molten material into a storage area or reservoir surrounding the heated electrode where such material is maintained in its uniformly heated molten state while further movement of the electrode into the workpiece(s) creates a cavity therein and, thereafter, retracting the heated electrode so as to permit the molten material to return to the cavity formed by the'electrode in the workpiece(s) where such molten material is allowed to cool and solidify,

thus forming a flawless bond between the workpieces and/or casting one or more workpieces in a predeter ,mined shape or form.

two or more workpieces together to form a unitary 'as- 'sembly where the bond is characterized-by its structural strength and/or, in some instances, by excellentcharac- 2 teristics -'of electrical conductivity. Yarious methods have been devised for bonding sucli workpieces tocussion welding, etc; i

' The particular technique pended upon many variable'parameters, including: (1)

in access to the region where the bonds are to be effected. Merely by way of example, in the battery-industry it is often necessary to-bond two ormore pieces fof lead together at various points, in some cases interiiall'y' and in others externallyof a given battery cell. Lead,

of course, is characterized by having arelatively low melting point on the order of only 630F., as contrasted with, for example, steel which has a melting point on the order of 3,000F.' Moreove -r where the lead workpieces'comprise battery straps, rplatesnterminal posts and/or intercell connectors, such as commonly em-.

ployed in industrial. motive-power batteries, automotive batteries, and the like, it is often difficult to gain access to the parts to be bonded, Even where access agents that can be utilized by virtue of other compo-.

nents present in the area of the bond toi beeffected such, for .example,.as the battery casing or cell jar whichis commonly made of rubber, the electrolytic selected has heretof re f acids present in or to be added to the battery cells, the

pasted positive and/or negative plates, the separators which are commonly made of microporous rubber, etc,

Many efforts have been made to devise improved bonding techniques which can be universally applied for the purpose of bonding two or more workpieces together irrespective by the wide range of variable p arameters mentioned above. Moreover, consistent with the demands of industry today, numerous efforts have been made to devise bonding techniques which are capable' of automation so as to enable. automatic bondin of multiple workpieces as an integrated part of massproduction line and/or assembly line techniques. Typi cal of the aforementioned approaches'a're those described in Us; Pat. N 5. 3,591,755, 3,608,809 and 3,706,126 of Robert 'I-Iolbrook Cushman, assigned to" the Western Electric Company, and relating to' 'i mechanical-thermalpulse continuous fusion bonding" 1' processes and apparatus which are based, at least in part, upon a combination of applied and controlled pressure and temperature to effect a desired bond.

Moreoven'despite'all such prior efforts which have have c'ontinued'to employ themore tedious, timeconsuming', manual bonding techniques which have 1 beenk-nown and utilized for many years. Typical of these is the industrial motive-power battery industry I where lead-to-lead bonds are still almost-universally .m'et with varying degrees of success, certain industries" I made by hand-torching *orhand-burning techniques].

employing oxyacetylene't'orche's and/or carbon burning tools. These techniques require highly skilledartisans,

of meeting the rigorous quality control standards set by the battery industry. Typical of the types of difficulties encountered even by such skilled artisans are: (1) nonuniform heating of the interface between the parts to be bonded resulting in no bonding at all at some locations, and/or burn-out of connectors and/or other parts because of over burning, thereby destroying the connector or other parts: (2) actual damage to and- /or destruction of the rubber casing or battery cover due to inadvertent direct application of the flame or carbon tip thereto: (3) lack of control over, and resultant non-uniformity of the depth of, bond penetration into the parts to be bonded, thereby resulting in bonds which are unsatisfactory from either or both of structural and/or electrical conductivity characteristics; and (4) substantially complete melting of one of the two or more parts to be bonded accompanied by failure to melt the surface of a second of the pieces to be bonded, thereby resulting in a cold-knit between the properly and improperly melted pieces.

As a direct result of the inability of certain industries-for example, the battery industryto utilize the aforementioned known automatic and semi-automatic bonding systems, and the continued industry-wide reliance on hand-torching and/or hand-burning techniques, numerous disadvantages have continued to plague su'ch industries. More specifically: (1) various industries, at great expense to themselves, have had to continue to attempt to train personnel in the difficult, time-consuming hand-torching or hand-burning techniques; (2) as a result of the relatively high heat generated by such techniques, the use of low melting point, economical, lightweight plastic battery casings has been precluded; (3) the percentage of batteries and/or battery cells rejected because of unsatisfactory bonds has remained high; and (4) the number of batteries which have passed rigorous quality control tests and/or procedures while having latent defects in the bonds has been unacceptably high, resulting in customer dissatisfaction because of the presence of leakers, particularly in the battery post/intercell connector, as well as an extremely objectionable phenomenon known in the art as electro-capillary action wherein battery electrolyte is actually pumped out of the battery cell through minute passages passing through the positive battery post/connector interface where the bond is defective, thereby not only weakening the cell affected and decreasing its life and usefulness, but often creating a direct short which drains the battery and which often causes corrosion and irreparable damage to other equipment in the immediate area.

OBJECTS OF THE INVENTION It is a general aim of the present invention to provide improved bonding and/or casting methods which overcome all of the foregoing disadvantages and which are characterized not only by their dependability and reliability in operation, but, also by their ability to continuously reproduce successive bonds having substantially identical characteristics and which meet the rigorous quality control standards set by the industry. More specifically, it is a principal aim of the invention to provide improved methods for forming metal-to-metal bonds which, when applied to the battery making industry, substantially eliminate, if not completely eliminate, the danger of leakers and/or electro-capillary action resulting from non-uniform bonding of the battery post- /intercell connector interface.

Another of the general objectives of the present invention is the provision of improved bonding and/or casting methods which can be readily introduced into existing production and/or assembly lines with only minimum revisions to, and interruption of, such lines.

An important object of the present invention is the provision of improved methods and apparatus for minimizing the presence of oxides and other contaminants in the immediate environment of the bond, as well as for minimizing the build-up of oxides on the bonding electrode.

More particularly stated, it is an object of the invention to provide for minimizing oxidation and build-up of oxides in the immediate environment of the bond and/or electrode, and for removing contaminants from the area of the bond.

These and other objects and advantages of the present invention will become more readily apparent upon reading the ensuing detailed description of the invention and upon reference to the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary exploded perspective view, here illustrating the various components present in a conventional lead-acid storage battery cell of the type commonly manufactured today and for many years past in the industrial motive-power battery industry.

FIG. 1 is a fragmentary perspective view, here illustrating the conventional and well-known technique of bonding an intercell connector with the use of a handheld carbon burning tool and a hand-held source of supplemental lead.

FIG. 3 is a vertical side elevation, partly in section, of a conventional battery cover, post, bushing and intercell connector assembly, here illustrating the parts prior to a hand-torching of hand-burning operation.

FIG. 4 is a perspective view of a portion of a positive displacement casting system embodying features of the present invention, here illustrating an industrial motive-power battery disposed on a conveyor beneath a bonding head positioned to automatically effect a bond between a lead battery post of one battery cell and an intercell connector.

FIG. 5 is a fragmentary perspective view taken generally at right angles to the view shown in FIG. 4 and here depicting other portions of the apparatus.

FIG. 6 is a plan view of the exemplary apparatus shown in FIG. 4, here depicting the bonding head over one conveyor belt and a battery positioned on the adjacent conveyor belt in readiness for a bonding operation.

FIG. 7 is an elevational view taken substantially along theline 77 of FIG. 6, here depicting the bonding head in solid lines disposed over a battery carried by the left-hand conveyor and in phantom lines over a battery carried by the right-hand conveyor.

FIG. 8 is a perspective view of the front of a control console utilized with the apparatus for carrying out the present invention, here depicting the console with its lower door open to expose the drawer containing certain of the electrical controls for the system.

FIG. 9 is an exploded perspective view, here illustrating particularly the relationship between a typical battery cover, post, bushing and intercell connector.

FIG. is an elevational view, partly in section, similar to FIG. 3, but here illustrating the various components of a battery post/intercell connector assembly, again depicting the parts prior to a bonding operation.

FIGS. 11a through lle are fragmentary, enlarged, simplified, and somewhat diagrammatic side elevational views, partly in section, here depicting the sequence of operations in a typical positive displacement casting operation embodying features of the present invention; FIG. 11a depicting the battery components to be bonded with the bonding head disposed above such components; FIG. 11b illustrating the bonding head properly located and locked in position in readiness to initiate a bonding operation; FIG. 11c illustrating the component parts of the system with the bonding ramlike electrode partially advanced into the workpieces to be bonded, and with the molten lead formed through this stage of the procedure having been displaced into surrounding relationship to the ram; FIG. 11d illustrating the component parts of the system with the ram-like electrode fully advanced into the workpieces to be bonded and with the molten lead formed having been displaced into surrounding relationship to the ram; and FIG. lle depicting the component parts of the system with the bonding head still in its down position but with the ram-like electrode retracted and with the molten lead having been returned to the cavity formed by the ram in the workpieces and having cooled and solidified to form a finished bond.

FIG. 12 is a fragmentary side elevation, partly in section, taken substantially along the line l212 in FIG. 6, here depicting particularly the supporting rail construction for the head which permits of movement of the head from a position above one conveyor to a position above the adjacent conveyor.

FIG. 13 is an enlarged plan view, partly in section, taken substantially along the line 13l3 in FIG. 7, and depicting certain of the clamping mechanism utilized to lock the bonding head in position.

FIG. 14 is an enlarged v'ertical sectional view taken substantially along the line 14-14 in FIG. 13, with certain parts removed for purposes of clarity, and illustrating the general relationship of parts in the bonding head.

FIG. 15 is a vertical elevational view, partly in section, similar to FIG. 14, but here taken substantially along the line 15-15 in FIG. 13 and at right angles to the view depicted in FIG. 14.

FIG. 16 is an enlarged fragmentary vertical sectional view depicting the lower end of the apparatus shown in FIG. 14, but here greatly enlarged to show details of the component parts of the equipment including the electrode cooling system and the inert gas flow system of the invention utilized to minimize oxidation.

FIGS. 17a and 17b are successive portions of a continuous strip chart depicting graphically in the upper and lower curves respectively the power output and the amperage of the system, both with respect to time, for a series of thirteen (l3) successive bonds, and illustrating particularly the undesired deviations in power and amperage as oxides build up on the ram-like electrode,

thus producing greater and greater arcing and, ultimately, a bum out of an intercell connector assembly.

FIG. 18 is a perspective view of a completed bonded assembly comprising a battery post, bushing and intercell connector, but wherein the resultant bond is defective and characterized by the presence of cold collars, cracks and crazing, and the presence of a concavity or saucer like configuration on the upper surface of the resultant bond, all of which are undesirable characteristics for intercell connector assemblies, particularly on industrial motive-power batteries.

SUMMARY OF THE INVENTION this, the present invention contemplates novel methods I wherein a heated ram-like electrode is moved coaxially through a reservoir defining means which, in the exemplary forms of the invention, comprises a co-axial barrel surrounding the electrode and defining therebetween an annular reservoir. The reservoir defining meanse.g., the barrelis first bottomed on one of the elements to be bonded in a position co-axial with the axis of the bond to be formed. Thereafter, the ram-like electrode is moved axially through the reservoir defining means into engagement with the workpiece or workpieces to be bonded where the heatdeveloped serves to convert the solid workpiece(s) to a molten state inthe area selected for the fusion bond. Continued axial advance of the electrode serves to progressively melt the portions of the workpieces along the axis of the bond area, which axis, of course, coincides with the axis of the electrode, and the molten material thus formed is displaced by the electrode in an annular column surrounding the electrode and within the reservoir defined between the electrode and the selected reservoir defining means. During movement of the electrode, the bond area is continually flushed with an inert gas to remove oxidants and to minimize build-up of oxides on the electrode itself When the ram-like electrode reaches'the limit of its advance movement, a limit that may be adjusted by the operator to provide for a bond for any desired depth, a short dwell period is provided to insure uniform heating of those portions of the workpieces immediately adjacent the cavity formed therein by displacement of voir defining means to a position out of contact with with the electrode-is retracted from its bottomed engagement with the workpieces, and the bond cycle is complete.

When dealing with workpieces formed of conductive metals, the activating circuit for the system is preferably from a suitable power source, through the movable electrode, through the conductive metal workpieces,

through the reservoir defining means, and back to the source. The power source may be either continuous or pulsating. When dealing with non-conductive workpiece materials, the movable ram-like electrode may simply comprise or contain a suitable resistance element or the like capable of attaining and maintaining a desired temperature level sufficient to melt that portion of the workpiece material which is to be displaced and subsequently returned to effect the desired fusion bond.

While the present invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. More specifically, the invention will hereinafter be described in connection with equipment for forming leadto-lead bonds and/or for positive displacement casting of lead, techniques that are particularly suitable for use in the industrial motive-power battery industry and, for that reason, the exemplary forms of the invention are described in connection with the making of such batteries. In its broadest aspects, however, it will be understood as the ensuing description proceeds that the inventionmay find many other applications outside of the battery making industry, outside of lead-to-lead fusion bonding techniques and, indeed, outside of metalto-metal fusion bonding techniques. Therefore, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as expressed in the appended claims.

THE ENVIRONMENT OF THE INVENTION As hereinabove explained, the present invention will be described herein in connection with methods and apparatus which find particularly, but by no means exclusive, application in the industrial motive-power battery industry. Accordingly, and as best seen by re ference to FIGS. 1, 2 and 3 conjointly, there have been depicted fragmentary portions of a typical industrial battery, generally indicated at 50 in FIG. 2, which is here composed of a plurality of individual battery cells 51. Such batteries may vary widely in size, configuration and electrical characteristics, and may, merely by way of example, range upwards of several feet in length, heighth and width and weigh upwards of several tons. Conversely, such batteries may be relatively small and may be capable of being transported by hand.

Referring more specifically to FIG. 1, a conventional battery cell 51 has been depicted in partially exploded form so as to expose most of the various battery components contained therein. Such components normally include a cell casing 52, commonly called a jar, and cover 54, both of which have heretofore conventionally been formed of high impact rubber. Contained within the cell casing 52 are a group of negative plates 55, a group of positive plates 56, and a group of separators 58. The negative plates 55 and positive plates 56 of the exemplary cell 51 comprise cast lead grids into which selected chemical pastes, or active materials, are inserted. Generally, a negative plate 55 may contain a paste consisting of a spongy lead material containing an expander to maintain the spongy condition, while the positive plates 56 may contain a paste consisting of lead oxide, sulfuric acid and water mixed to a putty-like consistency. After the pastes have been applied to the respective grids, the grids are dried. The positive plates 56 are normally wrapped with fiberglas or the like (not shown) to insure retention of the active materials, and each positive plate is then inserted into a plastic protective envelope, as best indicated at 59 (FIG. 1). The separators 58 are preferably formed of microporous rubber which is temperature and acid resistant, and are generally flat on the side adjacent the negative plate and grooved on the side adjacent a positive plate. Such separators 58 serve as insulators between the interleaved positive and negative plates, although they are sufficiently porous to permit free passage of electrolyte therethrough. v

After casting of the positive and negative plates, application of the active materials thereto, drying, and wrapping of the positive plates, positive and negative groups or assemblies of plates are formed, commonly by welding the lug portions 55a, 56a of the plates to battery straps and/or battery posts. As here shown, the negative plate lugs 550 are welded to a battery strap 60 integral with a pair of vertically upstanding, negative battery posts 61, while the positive plate lugs 56a are welded to a similar battery strap 62 integral with a pair of vertically upstanding positive battery posts 64. The thus assembled negative and positive plate groups are then interleaved with one another, there being a separator 58 between each positive and negative plate, and the entire assembly is inserted into the cell casing or jar 52 on top of a sediment bridge (not shown). A protective element 65, which may be made of plastic, is placed on top of the plate assembly so as to prevent: (1) foreign materials from entering the cell; (2) damage to the internal cell components by careless use of hydrometers or thermometers; and (3) moss shorts between the positive and negative plates. The high impact rubber cover 54 is then positioned on top of the jar or casing 52, with the posts 61 and 64 passing through lead bushings 66 molded in place in the cover, and the cover is secured to the jar by means of a hot, pliable, asphalt based compound. Normally at this stage of the assembly operation, the battery posts 61, 64 are bonded to the respective bushing inserts 66 by a handburning or hand-torching technique, electrolyte is added to the battery cell through a fill opening 68 adapted'to be closed by a screw-threaded tap 69, and the cell is then repetitively charged and discharged to assure proper capacity and quality.

Once the cells 51 have been assembled, charged and inspected, they are then ready to be assembled in various configurations to provide a complete battery 50 to meet specific requirements of a customer or ultimate user. In such assembly, multiple cells are inserted into a sheet battery casing 70 (FIG. 2) and interconnected in accordance with the requirements and specifications of the customer or user. Such interconnections commonly entail the use of lead intercell connectors 71 which bridge the space between battery posts of oppo- I tool 72 (which could, of course, be an oxyacetylene torch) is used to melt the inner rim 75 of the opening in the connector 71 surrounding the post/bushing combination and, at the same'time, to melt the exposed surface of the previously bonded post/bushing combination, with the molten lead thus formed being mixed or puddled by the hot tip of the tool 72. Additional lead is similarly melted by the tool 72 from the lower end of the supplemental lead rod 74 so as to provide sufficient molten lead to fill the entire cavity within the connector 71 defined by the edge 75 and surrounding the post- /bushing combination. Indeed, the workman will commonly place a conventional mold (not shown) about the work area so as to permitthe formation of a raised, button-like bond, as best indicated at 76 inFIG. 2.

It should be understood, that while it would be possible to create the aforementioned bond 76 in a single hand-burning or hand-torching operation by applying the tool 72 or torch to the assemblage of parts as shown in FIG. 3, the operation is most normally conducted in two stages-first bonding the post/bushing combination and later bonding the connector 71 to the previously bonded post/bushing combination. One reason for such two-stage bonding or torching procedure is simply that it is desirable that a permanent bond be created between the post 61 (64) and bushing 66 immediately after assembly and prior to introduction of electrolyte into the cell so as to prevent acid or other foreign materials from becoming lodged in the interface between the post and the bushing.

It will be immediately recognized by those skilled in the art that the hand-burning and/or hand-torching operations herein described have many disadvantages and are frought with dangers. Such procedures are slow, and require skilled personnel to carry them out. As lead is melted and puddled, it tends to cover the surfaces of the parts to be bonded, and extreme care must be taken to insure that all of the mating surfaces or interfaces to be bonded are uniformly heated and rendered moltenotherwise, molten lead contained within the puddle will tend to adhere to a surface which has not been capillary pumping action at the positive post. And, of

course, if extreme care is not taken, it is relatively easy to overheat the parts. When this occurs, the entire peripheral portion or rim 78 (FIG. 3) of the connector 71 a may berendered molten, permitting the puddle of lead to spill over the top of the cell, thereby destroying the ing; it has heretoforeib'een impractical to use'more economical and lightweight-materials such-as-plastic in the formation of -cell--casings=and/or covers because such materials commonly have much lower melting points than the hard impact rubber heretofore used.

. Posrr v E DISPILAC'EMEINT CASTING IN,

ACCORDANCE WITH T I-IE INVENTION I A. General Organization of ExemplarvApparatusn Referring owko F os. 4thrqugh8 inclusive, there has been illustrated an exemplary apparatusf'generally indicated at 100 n FIGS. 4 :7 for carrying out the present invention. As here shown, the exemplary apparatus 100 includesa positive displacement bonding means to move aselected conveyor 104; 105 in either' a forward or reverse direction, or 'to stop selected conveyor in a desired location'with a'battery '50 disposedbeneath the bondinghead'lO'l. Preferably the operator control 106 forms part of a suitable activating circuit (not shown) for conveyor 104, while control 108 forms part of an activating circuit for conveyor 105. To facilitate placement of batteries50 on, and re moval from; the conveyors, the batteries may be posiconnector parts and/or permitting burning of, and consequent damage ,to the rubber cover 54 Finally, be-

cause of the problems associated with such overheattioned on pallets 109 or the like which can be readily moved from place to place by conventional" fork-lifttrucks.

A-l. X-Oriented Movement f post locations ona" rapid,-pro'duction-line basis, the

overhead suspension system 102' is preferably'desig'rie d to permit of movement-of-the bonding head in both an X-oriented direction (transversely of the eonveyo'r as indicated by the arrows in FIGS. 4 "7) and.a 'Y= oriented direction (along the line of conveyoramove ment as indicated by the arrows in FIGS. '4' 6). To accomplishthis, the overhead suspension system 102 in 1 1 cludes a pair of parallel, spaced apartbeams 110, 111 (best illustrated in FIGS. 4 and 12) which extendtransversely-across both conveyors 104, and which we connected at their opposite ends by cross beams 112 114, (FIG. 6);'the beams 110, 111, 112and 114 defining a generally rectangular support structure (FIG. 6)? Vertically disposed, upright stanchio'ns 115 and 116' are permanently affixed at their upper ends-to thecross beamsl12, 114 respectively, and are mountedon the floor outboard of the conveyors 104, 105. The beams 1 10, 111 respectively support guide rails or tracks 118 119 which are parallel to the beams and also extend transversely across the conveyors 104,105. A carriage assembly, generally indicated at 120ir'i FIGS. 4and 7,

is provided'with suitable bearing sleeves 1 21 (FIG S.4

and 12) mounted in surrounding relation to the rails 118, 119,-therebypermittingslidable movement of the v i entire carriage assembly 1 20 -in.an '-'X.orie nted direction along the rails. Suitable lubricating means (not shown) may be provided so as to minimizefriction and thereby permit ease of movement of the carriage assembly 120 along the rails.

A-2 Y-Oriented Movement For the purpose of permitting movement of the bonding head 101 in a Y-oriented directioni.e., along the path of movement of the conveyors 104, lthe carriage assembly 120 is provided with a pair of depending support beams 122, 124 (best illustrated in FIG. 4) which here serve to support Y-oriented tracks or guide rails 125, 126, respectively. A sub-carriage assembly, generally indicated at 128, is slidably supported on the guide rails 125, 126 by means of bearing sleeves 129. Again, suitable lubricating means (not shown) may be provided for minimizing frictional resistance between the rails 125, 126 and bearing sleeves 129 so as to permit relatively easy movement of the sub-carriage assembly 128 along the Y-oriented guide rails 125, 126.

A-3. Z-Oriented Movement In carrying out the present invention, provision is made for enabling vertical movement of the bonding head 101 along a Z-oriented axis as viewed in FIGS. 4, 5 and 7. To this end, the various operating parts of the bonding head 101 was carried by a base plate 130 which is secured to the lower ends of a pair of vertically disposed support shafts 131, 132, such shafts passing upwardly through respective ones of a pair of bearing sleeves 134, 135 rigidly secured to a plate 136 which forms the undercarriage of sub-carriage assembly 128. The upper ends of the shafts 131, 132 have enlarged collars 138, 139 (FIG. 6; best illustrated in FIG. 14) respectively affixed thereto which serve as stops engageable with plate 136 to limit downward movement of the bonding head 101.

For the purpose of permitting the bonding head 101 to float during periods between bonding cycles and during movement of the head by the operator, and to further permit automatic movement of the operating parts of the bonding head during a bonding cycle, the illustrative apparatus is provided with a series of fluidoperated, preferably pneumatic, piston/cylinder combinations 140, 141, 142, the specific functions of which will hereinafter be described in somewhat greater detail, but which are described in considerably greater detail in the aforesaid copending applications of Robert Holbrook Cushman, Ser. No. 435,157, and Raymond L. Schenk, .lr., Ser. No. 435,178. Those interested in such detailed descriptions are referred to the aforesaid copending applications. For the purpose of the present description of the general organization of parts for the exemplary apparatus, it will suffice to say that the opposite sides of the piston within piston/cylinder combination 140 are pressurized so as to balance the weight of the components carried by base plate 130 and which comprise the bonding head 101, thereby permitting the head to float at whatever height or level it is positioned in.

A4. Operator Controlled Positioning of Bonding Head The arrangement is such that the operator wishes to move the bonding head 101 into a position in readiness to initiate a bonding cyclefor example, in readiness to bond a battery post/intercell connector combination such as generally indicated at 144 in FIGS. 4 and 5-it is merely necessary that he first activate the control 106 for conveyor 104 for, alternatively, control 108 for conveyor to generally locate a battery 50 beneath the bonding head 101. Having generally located a battery relative to the head, the operator next grasps one of the handles projecting laterally from the base plate 130 and shifts the bonding head 101 laterally in either or both of an X-oriented and or Y-oriented direction until the bonding ram assembly, generally indicated at 146 in FIGS. 4, 5 and 7, is accurately centered over the particularly battery post/intercell connector combination 144 to be bonded. The operator then needs only push downwardly on the handle 145 so as to urge the bonding head 151 and ram assembly 146 downwardly from the position shown in FIG. 7 to the position such as shown in FIGS. 4 and 5 where the particular battery post to be bonded projects co-axially upward into the bonding ram assembly 146 when the latter is bottomed on the intercell connector to be bonded. The operator is now ready to initiate a bonding cycle for the particular post/connector combination 144 located under the bonding ram assembly 146 and, when the bond is completed, the bonding head 101 will automatically move upward to the position shown in FIG. 7. The operator then again grasps the handle 145 and moves the bonding head 101 in either an X- or Y- oriented direction to a position over the next post/connector combination 144 to be bonded, and again repeats the foregoing operation.

A-5. Typical Battery Post, Bushing and Intercell Connector to be Bonded Referring next to FIGS. 9 and 10, there have been illustrated details of a typical organization of battery components particularly suitable for bonding in accordance with the present invention. More specifically, there is depicted a battery post/intercell connector combination 144 which consists of an upstanding lead battery path 148, a lead cover bushing 149 adapted to be molded directly into a battery or cell casing 150 (which may conveniently be made of plastic, hard impact rubber, or any other suitable material), and a lead intercell connector 151. The lower end of battery post 148 is, -as heretofore described, affixed to, or integral with, a battery plate strap 152 which serves to interconnect a plurality of battery plates of like polarity-either positive plates or negative plates. The arrangement is such that, when assembled prior to bonding as shown in FIG. 10, the battery post 148 passes co-axially upward through the lead bushing insert 149 and cover 150. The opposite ends of the lead intercell connector (one such end being visible in FIGS. 9 and 10) are each provided with a vertically disposed opening or passage 154 having a diameter sufficiently large to permit the connector 151 to be positioned in co-axial surrounding relation to an upstanding flange 155 formed on the bushing 151, with the lower surface of the connector in direct lead-to-lead contact with a horizontal or radial flange 156 formed on the bushing.

To insure concentricity of the parts and, at the same time, to provide for sound electrical contact therebetween, the lead battery post 148 may be provided with 

1. A method of casting meltable material comprising the steps of: a. moving a ram relative to the material so as to cause the ram to engage the material; b. establishing a reservoir surrounding the ram and engaged with the material to be cast; c. introducing a forming gas into the reservoir for the purpose of combining with and neutralizing oxidizing agents in the region of the material to be cast; d. heating the ram to a temperature sufficient to convert the meltable material in the path of relative ram movement to the molten state; e. moving the heated ram relative to the material and through the reservoir so as to cause the ram to melt the material in its path of relative movement and in the environment of the forming gas to a desired depth in the material with the molten material thus formed being displayed by the ram from the area of ram penetration into the material and shifted therefrom into the reservoir; and f. retracting the ram relative to the material from its position of miximum penetration so as to cause the ram to be withdrawn from the material; whereupon the molten material theretofore displaced into the reservoir is returned back to the region of ram penetration into the meltable material where such molten material is permitted to cool and solidify.
 2. The method as set forth in claim 1 further characterized in that said forming gas comprises a mixture of nitrogen and hydrogen.
 3. The method as set forth in claim 2 further characterized in thAt said mixture consists of on the order of 96 percent nitrogen and 4 percent hydrogen.
 4. The method as set forth in claim 1 further including the step of continuously introducing the forming gas into the reservoir during a casting operation.
 5. The method as set forth in claim 4 further including the step of continuously extracting the forming gas from the reservoir during the casting operation so as to entrain undesired oxidants, other contaminants and noxious fumes in the forming gas stream and to remove them from the immediate area of the ram and molten material.
 6. The method as set forth in claim 1 further characterized in that the meltable material comprises n (where n equals two or more) component parts adapted to be bonded together in a positive displacement casting, molecular fusion bonding process.
 7. The method as set forth in claim 6 further characterized in that said n component parts are formed of lead.
 8. The method as set forth in claim 7 further characterized in that said forming gas comprises a mixture of nitrogen and hydrogen.
 9. The method as set forth in claim 8 further characterized in that said mixture consists of on the order of 96 percent nitrogen and 4 percent hydrogen.
 10. The method as set forth in claim 7 further including the steps of continuously introducing the forming gas into and continuously extracting the forming gas from the reservoir during the bonding operation so as to entrain undesired oxidants, other contaminants, and noxious fumes in the forming gas stream and to remove them from the immediate area of the ram and the molten lead. 